Scientists combing through genetic data think they've worked out why some people have hair that just can't be tamed.
Named after a character in a German children's book with an unruly mop, 'Struwwelpeter syndrome' is rare - there have only been 100 documented cases since 1973.
Also known as "uncombable hair syndrome", scientists in Germany and France believe it's much more common than that.
"Those who suffer from uncombable hair do not necessarily seek help for this from a doctor or hospital," says Regina Betz of the Institute for Human Genetics at the University of Bonn.
But with the frizzy, dry, and usually blonde hair running in the family, Prof Getz realised the condition must be genetic.
She examined DNA collected from 11 children, and found three key genes responsible. One contains an important protein, which are joined to each other by strands of keratin. The other two genes control how the proteins and keratin fit together.
If just one of these genes is faulty, it messes up the hair.
"From the mutations found, a huge amount can be learned about the mechanisms involved in forming healthy hair, and why disorders sometimes occur," says Prof Betz.
"At the same time, we can now secure the clinical diagnosis of 'uncombable hair' with molecular genetic methods."
Struwwelpeter, in a 1917 edition of the children's book (Wikipedia)
There are some diseases that cause symptoms similar to Struwwelpeter syndrome. Prof Betz says knowing the genetic basis for it will help rule out other causes when someone's hair turns against them.
While uncombable hair might be tiresome and annoying, Prof Betz says "those affected have no need to otherwise worry".
The research was published Friday (NZ time) in the American Journal of Human Genetics.